Approved to Test

 "Who knows when thou mayest be tested? So live that thou bearest the strain!"

From "The Laws of the Navy", by Rear Admiral Hopwood

I've been through the routine of large exams: US Coast Guard Marine Engineer Licensing, twice, National Registry for Emergency Medical Technicians, and the NCEES' own Fundamentals of Engineering. Now, it's time for the Professional Engineering exam. 

In contrast to school exams, predictably scheduled,  professional exams occur based on the ebbs and flows of work experience, completion of prerequisites such as career training, and by the individual's own volition. So there is a general sense of when things will come together, but the "statutory" readiness occurs when it does. As for the individual readiness of studying, it's good to be prepared ahead of time, but to prevent knowledge attrition, the six-month period before the exam is critical. 

Which brings me to the point of scheduling the exam. Exams for certain desirable positions, such as high-end firefighting and ship's harbor pilots, only test twice a decade. More commonly, they might be twice-annually, as the Professional Engineering exams used to be. So you would typically schedule for the next exam available. And when there is flexible, daily test availability? Just schedule it and hold yourself to that date.